1. Field of the Invention
The present invention relates to gas laser apparatuses.
2. Description of the Related Art
Output efficiency of a gas laser apparatus decreases in accordance with a decrease in the purity of a laser gas enclosed in a receptacle. Although a receptacle of a gas laser apparatus is designed so as to be sealed substantially hermetically, a surrounding atmospheric gas may enter the receptacle in some cases. Therefore, a laser gas is replaced by discharging a gas from the receptacle to the outside and by refilling the receptacle with a laser gas, in order to increase the purity of a laser gas.
Japanese Laid-open Patent Publication No. 02-65187 discloses a laser gas replacing method in which a laser gas in a container is replaced periodically. According to this laser gas replacing method, the laser gas is exhausted from the container until the pressure inside the container reaches a predetermined pressure, and the exhausting process is terminated after the exhausting process is continued for a predetermined period of time.
Japanese Registered Utility Model No. 2561510 discloses a gas laser apparatus that includes a gas leak detecting device. The gas leak detecting device is configured to detect a gas leak during the time when the gas laser apparatus is stopped. Specifically, the gas leak detecting device disclosed in Japanese Registered Utility Model No. 2561510 stores the pressure of a laser gas prior to the power supply being turned off, and compares the pressure of a laser gas when the power supply is turned on again with the stored pressure of the laser gas. The gas leak detecting device then detects an occurrence of a gas leak on the basis of the result of the comparison.
With the laser gas replacing method disclosed in Japanese Laid-open Patent Publication No. 02-65187, however, the laser gas is replaced at a fixed cycle, and thus the laser gas is replaced even when the laser gas does not need to be replaced. Therefore, the amount of consumed laser gas increases, and the running cost of the gas laser apparatus increases. In addition, the gas laser apparatus needs to be put on standby until the replacement of a laser gas is completed, and thus the startup time of the gas laser apparatus tends to become longer. Furthermore, with the gas laser apparatus disclosed in Japanese Registered Utility Model No. 2561510, efficiency of the startup process of the gas laser apparatus is not taken into consideration.
Accordingly, there is a need for a gas laser apparatus in which a laser gas can be replaced as necessary, making it possible to reduce the startup time and to reduce the amount of consumed laser gas.